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Tue, 11 Aug 2026 16:29:43 +0200 (CEST) Date: Tue, 11 Aug 2026 16:29:34 +0200 From: Boris Brezillon To: Nicolas Frattaroli Cc: Steven Price , Liviu Dudau , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Grant Likely , Heiko Stuebner , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, kernel@collabora.com, Steven Rostedt Subject: Re: [PATCH v3 1/3] drm/panthor: Add tracepoints for cache flushing Message-ID: <20260811162934.340b1f16@fedora-21.home> In-Reply-To: <20260811-panthor-cache-flush-fix-v3-1-47d2c1bb1dab@collabora.com> References: <20260811-panthor-cache-flush-fix-v3-0-47d2c1bb1dab@collabora.com> <20260811-panthor-cache-flush-fix-v3-1-47d2c1bb1dab@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Tue, 11 Aug 2026 16:08:31 +0200 Nicolas Frattaroli wrote: > Add two new event tracepoints: gpu_cache_flush_start to be emitted after > acquiring the flush mutex and reqs spinlock, and gpu_cache_flush_end to > be emitted when leaving the function. > > This allows debugging the duration a flush takes irrespective of initial > function entry lock contention by subtracting the start tracepoint's > timestamp from the end tracepoint timestamp, and additionally contains > information such as which caches were flushed. > > Reviewed-by: Steven Rostedt > Reviewed-by: Liviu Dudau > Reviewed-by: Steven Price > Signed-off-by: Nicolas Frattaroli > --- > drivers/gpu/drm/panthor/panthor_gpu.c | 7 ++++- > drivers/gpu/drm/panthor/panthor_trace.h | 49 +++++++++++++++++++++++++++++++++ > 2 files changed, 55 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/panthor/panthor_gpu.c b/drivers/gpu/drm/panthor/panthor_gpu.c > index c013d6bf9a59..68e2dd2527df 100644 > --- a/drivers/gpu/drm/panthor/panthor_gpu.c > +++ b/drivers/gpu/drm/panthor/panthor_gpu.c > @@ -337,6 +337,7 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > guard(mutex)(&ptdev->gpu->cache_flush_lock); > > spin_lock_irqsave(&ptdev->gpu->reqs_lock, flags); > + trace_gpu_cache_flush_start(ptdev->base.dev, l2, lsc, other); > if (!(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED)) { > ptdev->gpu->pending_reqs |= GPU_IRQ_CLEAN_CACHES_COMPLETED; > gpu_write(gpu->iomem, GPU_CMD, GPU_FLUSH_CACHES(l2, lsc, other)); > @@ -345,8 +346,10 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > } > spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags); > > - if (ret) > + if (ret) { > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other); I don't mind having start/end traces, but I still think it'd be valuable to report failure cases. > return ret; > + } > > if (!wait_event_timeout(ptdev->gpu->reqs_acked, > !(ptdev->gpu->pending_reqs & GPU_IRQ_CLEAN_CACHES_COMPLETED), > @@ -360,6 +363,8 @@ int panthor_gpu_flush_caches(struct panthor_device *ptdev, > spin_unlock_irqrestore(&ptdev->gpu->reqs_lock, flags); > } > > + trace_gpu_cache_flush_end(ptdev->base.dev, l2, lsc, other); > + > if (ret) { > panthor_device_schedule_reset(ptdev); > drm_err(&ptdev->base, "Flush caches timeout"); > diff --git a/drivers/gpu/drm/panthor/panthor_trace.h b/drivers/gpu/drm/panthor/panthor_trace.h > index 6ffeb4fe6599..6951b95b1de7 100644 > --- a/drivers/gpu/drm/panthor/panthor_trace.h > +++ b/drivers/gpu/drm/panthor/panthor_trace.h > @@ -76,6 +76,55 @@ TRACE_EVENT(gpu_job_irq, > __entry->events, __entry->duration_ns) > ); > > +DECLARE_EVENT_CLASS(gpu_cache_flush_template, > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other), > + TP_ARGS(dev, l2, lsc, other), > + TP_STRUCT__entry( > + __string(dev_name, dev_name(dev)) > + __field(u32, l2) > + __field(u32, lsc) > + __field(u32, other) > + ), > + TP_fast_assign( > + __assign_str(dev_name); > + __entry->l2 = l2; > + __entry->lsc = lsc; > + __entry->other = other; > + ), > + TP_printk("%s: l2=0x%x lsc=0x%x other=0x%x", __get_str(dev_name), > + __entry->l2, __entry->lsc, __entry->other) > +); > + > +/** > + * gpu_cache_flush_start - called after cache flush locks taken, before flush > + * @dev: pointer to the &struct device, for printing the device name > + * @l2: "l2" flush flags > + * @lsc: "lsc" flush flags > + * @other: "other" flush flags > + * > + * Fires after any initial lock contention around the locks needed for flushing > + * caches, but before the actual cache flush is requested. > + */ > +DEFINE_EVENT(gpu_cache_flush_template, gpu_cache_flush_start, > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other), > + TP_ARGS(dev, l2, lsc, other) > +); > + > +/** > + * gpu_cache_flush_end - called after cache flush > + * @dev: pointer to the &struct device, for printing the device name > + * @l2: "l2" flush flags > + * @lsc: "lsc" flush flags > + * @other: "other" flush flags > + * > + * Fires after either the cache flush is complete, or has failed. Can be used > + * together with gpu_cache_flush_start to get how long the flush has taken. > + */ > +DEFINE_EVENT(gpu_cache_flush_template, gpu_cache_flush_end, > + TP_PROTO(const struct device *dev, u32 l2, u32 lsc, u32 other), > + TP_ARGS(dev, l2, lsc, other) > +); > + > #endif /* __PANTHOR_TRACE_H__ */ > > #undef TRACE_INCLUDE_PATH >